The present invention relates to microelectronic devices and more particularly to light emitting diodes.
Light emitting diodes (LEDs) are widely used in consumer and commercial applications. As is well known to those having skill in the art, a light emitting diode generally includes a diode region on a microelectronic substrate. The microelectronic substrate may comprise, for example, gallium arsenide, gallium phosphide, alloys thereof, silicon carbide and/or sapphire. Continued developments in LEDs have resulted in highly efficient and mechanically robust light sources that can cover the visible spectrum and beyond. These attributes, coupled with the potentially long service life of solid state devices, may enable a variety of new display applications, and may place LEDs in a position to compete with the well entrenched incandescent and fluorescent lamps.
To increase the output of LEDs, several approaches have been utilized. Two such approaches include increasing the size of the LEDs and connecting multiple discrete LEDs in parallel. Increasing the size of the LEDs may provide increased output by increasing the light emitting area of the LED. However, as size increases, yields typically decrease. Furthermore, light extraction may be more difficult as the size of the LED increases. Thus, increasing the size of the LED may increase the cost of the LED in relation to the amount of light produced by the LED.
Providing multiple discrete LEDs which have been individually tested and interconnected may overcome the yield issues of increased size LEDs as well as problems with extraction of light from the LEDs. However, individually testing, matching and/or interconnecting the multiple LEDs may increase the cost of the product.
Embodiments of the present invention provide methods of forming a light emitting diode by scoring a semiconductor substrate having a light emitting region formed thereon so as to provide score lines between individual ones of a plurality of light emitting diodes. The semiconductor substrate is then separated along selected ones of the score lines so as to provide a unitized subset of the plurality of light emitting diodes. The unitized subset includes at least two light emitting diodes. Electrical connections are provided to the light emitting diodes of the unitized subset of the plurality of light emitting diodes.
In further embodiments of the present invention, the score lines define individual ones of the plurality of light emitting diodes.
In particular embodiments of the present invention, the semiconductor substrate comprises a silicon carbide substrate. Alternatively, the semiconductor substrate may be a sapphire substrate.
In still further embodiments of the present invention, the selected ones of the score lines along which the semiconductor substrate is broken are score lines that provide a strip of light emitting diodes. Furthermore, the selected ones of the score lines along which the semiconductor substrate is broken may be score lines that provide a rectangle of light emitting diodes having at least two parallel rows of light emitting diodes. Similarly, the selected ones of the score lines along which the semiconductor substrate is broken may be score lines that provide a square of light emitting diodes.
Additionally, electrical connections may be provided by soldering to contacts of the light emitting diodes. The light emitting diodes may have a common contact for each of the light emitting diodes in the unitized subset and individual contacts corresponding to each of the light emitting diodes in the unitized subset. In such embodiments, electrical connections may be provided by providing a common connection for the common contact and providing a series-parallel connection of the individual contacts. The common connection may be provided by soldering a connection to the common contact. The parallel connection may be provided by connecting each of the individual contacts to a conducting bus strip. Such a parallel connection may also be provided by connecting a first of the individual contacts to a conducting bus and daisy-chaining remaining ones of the individual contacts to the first of the individual contacts.
In additional embodiments of the present invention, the selected ones of the score lines along which the semiconductor substrate is broken are score lines selected to provide a unitized subset of light emitting diodes that provided a selected wavelength profile. The selected wavelength profile may be a selected range of wavelengths.
In other embodiments of the present invention, the selected ones of the score lines along which the semiconductor substrate is broken are score lines selected to provide a unitized subset of light emitting diodes that provided a selected light output level.
In additional embodiments of the present invention, the score lines provide an ATON shape to each of the light emitting diodes.
In still further embodiments of the present invention, electrical connections to light emitting diodes of the unitized subset of the plurality of light emitting diodes are provided to selectively connect the light emitting diodes of the unitized subset of the plurality of light emitting diodes so as to provide a set of light emitting diodes having a predefined characteristic. The predefined characteristic may be a light output characteristic and/or an electrical characteristic, such as a forward bias voltage.